Safe deposit boxes are generally unlocked by simply inputting a password or using only identity recognition, which is easier to crack passwords thereof. For example, unlocking software developed by many high-tech thieves can test combinations of passwords by running a program at a high speed to find out a correct unlocking password in a short period of time, i.e., realizing password cracking in the short period of time. Low-end thieves are more likely to guess the password in a short period of time, i.e., realizing password cracking, even though they manually test each digit of the password. Therefore, there is a very high risk of theft and the security needs to be improved.